Five Fascinating Facts About… Fall Monarch Migration

No one knows for sure just how or why monarchs undertake their massive migration, the only one like it in the butterfly world. Their fall journey is currently underway, so it’s the perfect time to learn a little more about these fascinating flyers.

Not all monarchs migrate. While most North American monarchs undertake amazing migrations each year, there are many monarchs in other parts of the world that do not migrate at all. Monarchs resident in Florida from around Orlando south do not need to migrate, as the climate allows their nectar and host plants to grow year-round. The same goes for Monarchs in Central and South America, the Caribbean, and other places around the world where monarchs live. That actually makes the North American monarch populations unique in their migratory behavior.

There are two groups of monarchs in North America that migrate to separate winter locations. Those living east of the Rocky Mountains generally migrate south to Mexico, while those living west of the Rockies move west to California. The most famous wintering grounds in the Oyamel Fir Forests of Central Mexico. The climate of these forests is not as tropical as many might expect, as they are high in the mountains, with daytime temps around 65 degrees or so and nights in the 30s. Monarchs that migrate west winter along the central and southern coast of California, in groves of eucalyptus trees. (Get a list of California over-wintering sites here.)

Monarchs don’t migrate south for food. When they arrive in their wintering grounds, these butterflies enter a state called “diapause”, which means that they do not eat or reproduce. Instead, they join together in huge roosting groups, so numerous that tree branches have been known to break under their weight, and stir themselves only to seek water on sunny days. They exist otherwise on stores of fat they accumulate along their journey south.

Migration peaks in September and October. The further north the monarchs are, the sooner they must begin their southward journey. Monarchs in Canada will begin moving south as early as August, but the largest numbers are usually seen in the middle of the country through September and October. You can track their journey and report your own sightings at the Journey North website. The butterflies take several months to make their journey south, which can be well over 2,000 miles depending on how far north they started, and it’s extremely important for them to eat as much as they can along the way. Be sure to have plenty of nectar plants available for butterflies well into the fall. You’ll recognize migrating groups when you see large numbers gathered together on nectar plants, or flying purposefully in a southern direction.

Cheery Chickadee – Keep lots of nectar plants available in your garden, as these monarchs need to build up fat stores for the winter in Mexico. It’s no longer necessary to worry about milkweed, though, since this generation won’t breed until their return trip in spring. Good luck with your spottings!

A couple of interesting facts that hardly anybody is aware of.
The southern monarch of South America (Danaus erippus) is a sister species of the northern one; only recently recognized as a different species. It migrates in a strange way: “The butterflies also fly south in the autumn along the eastern edge of the Andes Mountains in Argentina, a very puzzling phenomenon that takes them to colder latitudes for the winter.” According to National Geographic. Read more: http://newswatch.nationalgeographic.com/2011/04/06/monarch-butterflies-pictures-milkweed-advice/
Another remarkable migrant is a moth, not a butterfly. It leaves the monarch in the dust. The hummingbird hawkmoth (Macroglossum stellatarum) of Europe, Asia and Africa covers a geographic range much wider than the monarch and travels impressive distances. Look at the map in Wikipedia. http://en.wikipedia.org/wiki/Hummingbird_hawk_moth
It is time that we take our amazement to other levels.

I am surprised this year. I plant several butterfly gardens and plenty of milkweed, yet, this year in particular, there are very few Monarchs at least in my neighborhood. Lots of red admirals. In RI. have seen them prior seasons well into October to hatch and fly off.

I’m seeing migrating monarchs in Minneapolis. They are feeding mostly on tropical milkweed nectar, with some stops on zinnia, cleome, and lantana flowers. We have other nectar plants, too, but I haven’t see the monarch butterflies using them. Hummingbirds also seem to prefer the tropical milkweed.

I have had great success with my swamp milkweed bush! It has 11 stalks on it! My other milkweed plants have had eggs laid on them and caterpillars hatch!
I have had several Monarchs spend many days before moving on here in St. Louis MO!!

I live in Santa Barbara, CA where one of the monarch wintering spots resides and as of today (August 27th, 2014) my milkweeds plants are still teeming with eggs and caterpillars. I’m trying to maintain my milkweed plants as best as possible, while mass planting various milkweed seeds that are native to California. Hopefully my garden will be ready for the next Spring reproductive cycle 🙂